[0001] This application claims priority to Chinese Patent Application No.
201710487270.3, filed with the China National Intellectual Property Administration on June 23, 2017
and entitled "DATA TRANSMISSION METHOD, COMMUNICATIONS DEVICE, AND DATA TRANSMISSION
SYSTEM", which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to the communications field, and more specifically,
to a data transmission method, a communications device, and a data transmission system.
BACKGROUND
[0003] In a wireless communications system, when user equipment is located on an edge of
a network coverage area, or when interference of an ambient environment of the user
equipment to a network service is relatively great, network service quality of the
user equipment is usually relatively low. Therefore, a base station can send data
to the user equipment by performing a plurality of retransmissions, or even cannot
send the data to the user equipment by performing a plurality of retransmissions.
SUMMARY
[0004] In view of this, this application provides a data transmission method, a communications
device, and a data transmission system, to increase a success probability of data
transmission and reduce a probability of retransmission by a network side device to
user equipment.
[0005] According to first aspect, an embodiment of the present invention provides a data
transmission method. The method includes: receiving, by a cooperation device, to-be-transmitted
data sent by a network side device to a cooperation group, where the cooperation group
includes the cooperation device and a target device; and sending, by the cooperation
device, the to-be-transmitted data to the target device before a first moment, where
a moment at which the target device feeds back, to the network side device, whether
the to-be-transmitted data is correctly received is defined as the first moment. A
moment at which the cooperation device sends the to-be-transmitted data to the target
device is defined as a second moment. Duration between the second moment and the first
moment is greater than or equal to duration required by the target device to receive,
process, and check the to-be-transmitted data sent by the cooperation device.
[0006] In the method provided in the first aspect, even if the target device cannot correctly
receive the to-be-transmitted data sent by the network side device, if the target
device can correctly receive the to-be-transmitted data forwarded by the cooperation
device, the target device does not need to request the network side device to retransmit
the to-be-transmitted data, which can effectively improve a success probability that
the target device receives data, and reduce a probability that the network side device
performs retransmission to the target device.
[0007] According to the first aspect, in a first possible implementation of the data transmission
method, the cooperation device sends the to-be-transmitted data to the target device
by using a sidelink between the cooperation device and the target device. A frequency
band used for transmission on the sidelink is a licensed frequency band or an unlicensed
frequency band. The unlicensed frequency band has low use costs, does not cause interference
to communication between the network side device and the target device or the cooperation
device, and does not occupy a valuable licensed frequency band resource.
[0008] According to the first aspect, in a second possible implementation of the data transmission
method, when the unlicensed frequency band is used for transmission on the sidelink,
a channel used for transmission on the sidelink includes one or more candidate sidelink
channels. The method further includes: receiving, by the cooperation device in a common
sidelink subframe, information used to indicate whether the target device correctly
receives the to-be-transmitted data, where the common sidelink subframe is a subframe
at a preset location that is on the sidelink channel and that is agreed on between
the target device and the cooperation device. The method further includes: if the
cooperation device receives, before completing sending of the to-be-transmitted data
to the target device, information used to indicate that the target device correctly
receives the to-be-transmitted data, abandoning, by the cooperation device, sending
the to-be-transmitted data to the target device. Therefore, the cooperation device
can timely learn by using the common sidelink subframe, an ACK fed back by the target
device, and does not need to send the to-be-transmitted data to the target device,
thereby effectively reducing a spectrum resource.
[0009] According to the first aspect or the first possible implementation of the first aspect,
in a third possible implementation of the data transmission method, the method further
includes: sensing, by the cooperation device, the sidelink channel, and when sensing
an available sidelink channel, determining whether duration between a current moment
and a moment corresponding to a next common sidelink subframe is greater than or equal
to duration required for sending the to-be-transmitted data. When the duration between
the current moment and the moment corresponding to the next common sidelink subframe
is greater than or equal to the duration required for sending the to-be-transmitted
data, the step of sending, by the cooperation device, the to-be-transmitted data to
the target device is performed. When the duration between the current moment and the
moment corresponding to the next common sidelink subframe is less than the duration
required for sending the to-be-transmitted data, before the next common sidelink subframe,
the cooperation device abandons sending the to-be-transmitted data to the target device,
and after the next common sidelink subframe, performs the step of sending, by the
cooperation device, the to-be-transmitted data to the target device.
[0010] According to the first aspect or any one of the implementations of the first aspect,
in a fourth possible implementation of the data transmission method, the cooperation
device receives cooperation control signaling sent by the network side device or the
target device, where the cooperation control signaling indicates a cooperation policy.
Alternatively, the cooperation device determines the cooperation policy based on a
rule agreed with the target device. The cooperation policy includes a used cooperation
mode and parameters specifically used in the cooperation mode.
[0011] According to a second aspect, a data transmission method is provided. The method
includes: receiving, by a target device, to-be-transmitted data sent by a network
side device to a cooperation group, where the cooperation group includes a cooperation
device and the target device; receiving, processing, and checking, by the target device
before a first moment, the to-be-transmitted data sent by the cooperation device.
A moment at which the target device feeds back, to the network side device, whether
the to-be-transmitted data is correctly received is defined as the first moment.
[0012] In the method provided in the second aspect, even if the target device cannot correctly
receive the to-be-transmitted data sent by the network side device, if the target
device can correctly receive the to-be-transmitted data forwarded by the cooperation
device, the target device does not need to request the network side device to retransmit
the to-be-transmitted data, which can effectively improve a success probability that
the target device receives data, and reduce a probability that the network side device
performs retransmission to the target device.
[0013] According to the second aspect, in a first possible implementation of the data transmission
method, a moment at which the target device receives the to-be-transmitted data sent
by the network side device is defined as a third moment. The target device has at
least one subframe that is between the third moment and the first moment and that
is not used to process the to-be-transmitted data sent by the network side device.
When the mode is used, a TTI used for transmission on a sidelink between the cooperation
device and the target device may not be changed, so that cooperation transmission
may be implemented without increasing processing complexity.
[0014] According to the second aspect or the first possible implementation of the second
aspect, in a second possible implementation of the data transmission method, the target
device receives, by using a sidelink between the target device and the cooperation
device, the to-be-transmitted data sent by the cooperation device. A frequency band
used for transmission on the sidelink is a licensed frequency band or an unlicensed
frequency band. The unlicensed frequency band has low use costs, does not cause interference
to communication between the network side device and the target device or the cooperation
device, and does not occupy a valuable licensed frequency band resource.
[0015] According to the second aspect or the first possible implementation of the second
aspect, in a third possible implementation of the data transmission method, when the
unlicensed frequency band is used for transmission on the sidelink, a channel used
for transmission on the sidelink includes one or more candidate sidelink channels.
The method further includes: sending, by the target device in a common sidelink subframe,
information used to indicate whether the to-be-transmitted data is correctly received.
The common sidelink subframe is a subframe at a preset location that is on the sidelink
channel and that is agreed on between the target device and the cooperation device.
Therefore, the cooperation device can timely learn by using the common sidelink subframe,
an ACK fed back by the target device, and does not need to send the to-be-transmitted
data to the target device, thereby effectively reducing a spectrum resource. The method
further includes: separately sensing, by the target device on each candidate sidelink
channel, the to-be-transmitted data sent by the cooperation device.
[0016] According to the second aspect or any one of the implementations of the second aspect,
in a fourth possible implementation of the data transmission method, the target device
receives cooperation control signaling sent by the network side device. The cooperation
control signaling indicates a cooperation policy. Alternatively, the target device
determines the cooperation policy based on a rule agreed with the cooperation device.
[0017] According to any one of the first aspect, the second aspect, or the foregoing implementations,
in another possible implementation, a transmission time interval TTI used for transmission
between the cooperation device and the target device is less than a TTI used for transmission
between the target device and the network side device. When the mode is used, cooperation
transmission can be quickly implemented without changing HARQ feedback duration and
HARQ process of the target device for the to-be-transmitted data sent by the network
side device, and without increasing a latency. A TTI 1 may be enabled to be less than
a TTI 2 in the following manners.
[0018] Manner 1: A quantity of symbols included in a subframe corresponding to the TTI 1
is less than a quantity of symbols included in a subframe corresponding to the TTI
2.
[0019] A smaller quantity of symbols in a subframe indicates a smaller subframe length.
Therefore, a corresponding TTI is smaller.
[0020] Manner 2: A length of the symbols included in the subframe corresponding to the TTI
1 is less than a length of the symbols included in the subframe corresponding to the
TTI 2.
[0021] According to a third aspect, a communications device is provided. The communications
device includes a processor and a transceiver. The transceiver is configured to receive
to-be-transmitted data sent by a network side device to a cooperation group, where
the cooperation group includes the communications device and a target device. The
processor is configured to control the transceiver to send the to-be-transmitted data
to the target device before a first moment. A moment at which the target device feeds
back, to the network side device, whether the to-be-transmitted data is correctly
received is defined as the first moment. A moment at which the transceiver sends the
to-be-transmitted data to the target device is defined as a second moment. Duration
between the second moment and the first moment is greater than or equal to duration
required by the target device to receive, process, and check the to-be-transmitted
data sent by the transceiver.
[0022] In the communications device provided in the third aspect, even if the target device
cannot correctly receive the to-be-transmitted data sent by the network side device,
if the target device can correctly receive the to-be-transmitted data forwarded by
the communications device, the target device does not need to request the network
side device to retransmit the to-be-transmitted data, which can effectively improve
a success probability that the target device receives data, and reduce a probability
that the network side device performs retransmission to the target device.
[0023] According to a fourth aspect, a communications device is provided. The communications
device includes a processor and a transceiver. The transceiver is configured to receive
to-be-transmitted data sent by a network side device to a cooperation group, where
the cooperation group includes a cooperation device and the communications device.
The transceiver is further configured to receive the to-be-transmitted data sent by
the cooperation device. The processor is configured to process and check, before a
first moment, the to-be-transmitted data sent by the cooperation device. A moment
at which the communications device feeds back, to the network side device, whether
the to-be-transmitted data is correctly received is defined as the first moment.
[0024] In the communications device provided in the fourth aspect, even if the communications
device cannot correctly receive the to-be-transmitted data sent by the network side
device, if the communications device can correctly receive the to-be-transmitted data
forwarded by the cooperation device, the communications device does not need to request
the network side device to retransmit the to-be-transmitted data, which can effectively
improve a success probability that the communications device receives data, and reduce
a probability that the network side device performs retransmission to the communications
device.
[0025] According to a fifth aspect, a communications system is provided. The system includes
the communications device according to the third aspect and the communications device
according to the fourth aspect.
[0026] According to still another aspect of this application, a computer-readable storage
medium is provided. The computer-readable storage medium stores a computer software
instruction used by the communications device according to the third aspect. When
the computer software instruction is run on a computer, the computer performs the
methods according to the foregoing aspects.
[0027] According to still another aspect of this application, a computer-readable storage
medium is provided. The computer-readable storage medium stores a computer software
instruction used by the communications device according to the fourth aspect. When
the computer software instruction is run on a computer, the computer performs the
methods according to the foregoing aspects.
BRIEF DESCRIPTION OF DRAWINGS
[0028]
FIG. 1 is an example schematic diagram of a communications system according to an
embodiment of the present invention;
FIG. 2 is an example flowchart of a data transmission method according to an embodiment
of the present invention;
FIG. 3 is an example schematic diagram of a faster cooperation mode according to an
embodiment of the present invention;
FIG. 4 is an example schematic diagram of a longer cooperation mode according to an
embodiment of the present invention;
FIG. 5 is another example flowchart of a data transmission method according to an
embodiment of the present invention;
FIG. 6A, FIG. 6B, FIG. 6C, and FIG. 6D are example schematic diagrams of user cooperation
according to an embodiment of the present invention;
FIG. 7A, FIG 7B, FIG. 7C, and FIG. 7D are example schematic diagrams of user cooperation
according to an embodiment of the present invention;
FIG. 8 is an example schematic structural diagram of hardware of a communications
device according to an embodiment of the present invention; and
FIG. 9 is an example schematic structural diagram of hardware of a communications
device according to another embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0029] The following describes the technical solutions in the embodiments of the present
invention with reference to the accompanying drawings in the embodiments of the present
invention.
[0030] The technical solutions in the embodiments of the present invention that are described
below are applicable to a communications system. The communications system may include
a network side device and at least two terminal devices that communicate with the
network side device. Two or more terminal devices may also communicate with each other.
FIG. 1 shows an example of the communications system. The communications system shown
in FIG. 1 includes one network side device (a gNB shown in FIG. 1) and a plurality
of terminal devices (CUE 1, CUE 2, and TUE shown in FIG. 1) that communicate with
the network side device.
[0031] The network side device may be a device that can communicate with user equipment.
The network side device may be, for example, a base station (a macro base station,
a small cell/a micro base station, a home base station, or the like), a relay station,
or an access point. The base station may be, for example, a base transceiver station
(base transceiver station, BTS) in a global system for mobile communications (global
system for mobile communication, GSM) or a code division multiple access (code division
multiple access, CDMA) network, or may be an NB (NodeB) in wideband code division
multiple access (wideband code division multiple access, WCDMA), or may be an eNB
or an eNodeB (Evolutional NodeB) in long term evolution (long term evolution, LTE),
or may be a gNB in a future 5G network or a new radio (new radio, NR). The network
side device may alternatively be, for example, a transmission reception point (transmission
reception point, TRPx) in a network. The network side device may alternatively be,
for example, a radio controller in a cloud radio access network (cloud radio access
network, CRAN) scenario. The network side device may alternatively be, for example,
an access point (access point, AP) in WiFi. The network side device may alternatively
be, for example, a wearable device or a vehicle-mounted device.
[0032] The terminal device may be user equipment (User Equipment, UE), an access terminal,
a subscriber unit, a subscriber station, a mobile station, a mobile console, a remote
station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless
communications device, a user agent, a user apparatus, or the like. The access terminal
may be a cellular phone, a cordless phone, a session initiation protocol (Session
Initiation Protocol, SIP) phone, a wireless local loop (Wireless Local Loop, WLL)
station, a personal digital assistant (Personal Digital Assistant, PDA), a handheld
device with a wireless communication function, a computing device or another processing
device connected to a wireless modem, a vehicle-mounted device, a wearable device,
a terminal device in a future 5G network, a terminal device in a future evolved PLMN
network, or the like.
[0033] When a specific terminal device is located on an edge of a network coverage area
or interference of an ambient environment to a network service is relatively great,
network service quality of the terminal device is relatively low. For example, a target
device TUE in FIG. 1 is located on an edge of a network coverage area. The network
device gNB is very likely to fail to send downlink data to the TUE, and therefore
a retransmission is caused. As shown in FIG. 1, because cooperation devices CUE (CUE
1 and CUE 2 shown in FIG. 1) are closer to the gNB, and network service quality between
the CUE and the gNB is relatively good, the CUE may cooperate with the gNB to send
data to the TUE. In this case, the technical solutions provided in the embodiments
of the present invention are as follows: A target device and at least one cooperation
device are configured to constitute a cooperation group. When the network side device
gNB needs to send data to the target device, the network side device sends the data
to the cooperation group, and both the cooperation device and the target device in
the cooperation group can receive the data. Because the target device is located on
an edge of a network area, the target device may fail to receive the data. However,
network service quality of the cooperation device is relatively good. Therefore, the
cooperation device is very likely to correctly receive the data. It is assumed that
a moment at which the target device feeds back, to the network side device, whether
the data (ACK/NACK) is correctly received is defined as a first moment. The cooperation
device may forward the received data to the target device before the first moment
by using a sidelink, and the target device only needs to receive, process, and check,
before the first moment, the data sent by the cooperation device. Therefore, even
if the target device cannot correctly receive the data sent by the network side device,
if the target device can correctly receive, before the first moment, the data forwarded
by the cooperation device, the target device does not need to feed back a NACK at
the first moment, but only needs to feed back an ACK. In this case, the network side
device does not need to retransmit the data. The technical solutions provided in the
embodiments of the present invention may help the network side device send data to
the target device, increase a success probability of data transmission, and reduce
a probability that the network side device performs retransmission to user equipment.
It may be understood that the cooperation device and the target device may be the
terminal devices described above. In the embodiments of the present invention, to
help distinguish between the terminal devices, the terminal devices may be separately
referred to as the cooperation device and the target device. It may be understood
that this is merely an example description.
[0034] An embodiment of the present invention provides a data transmission method. In the
embodiments of the present invention, an example in which a network side device needs
to send data to a target device and a cooperation device helps the network side device
send data to the target device is used for description. As shown in FIG. 2, in a first
embodiment of the data transmission method, the method includes the following steps.
[0035] S100. The network side device sends to-be-transmitted data to a cooperation group.
The cooperation group includes a cooperation device and a target device, and there
is at least one cooperation device. For example, as shown in FIG. 1, there are two
cooperation devices.
[0036] In an embodiment, the cooperation group may be configured by the network side device.
The network side device may determine the cooperation device and a cooperation group
identifier for the target device based on a communication status or a request of the
target device. The network side device sends the cooperation group identifier to the
target device and the cooperation device. The network side device further sends a
target device identifier to the cooperation device.
[0037] In another embodiment, the target device may initiate establishment of the cooperation
group. The target device may first initiate a request to the network side device,
and the network side device delivers the cooperation group identifier to the target
device. The target device may notify the cooperation device of the cooperation group
identifier by using a sidelink (Sidelink) established between the target device and
the cooperation device. The sidelink may also be referred to as a D2D (Device to Device,
device-to-device) link, an M2M (Machine to Machine) link, a terminal straight-through
link, an end-to-end link, a sidelink, or the like.
[0038] The sidelink between the target device and the cooperation device may be preestablished.
Alternatively, the target device and the cooperation device negotiate with each other
(for example, D2D discovery and D2D synchronization) to establish the sidelink. For
example, if the cooperation device receives a synchronization signal of the target
device, synchronizes with the target device, and receives information sent by the
target device, it may be considered that the sidelink is established between the target
device and the cooperation device. Alternatively, by using the D2D discovery, the
target device discovers the cooperation device, and the cooperation device agrees
to be discovered. In this case, it may be considered that the sidelink is established
between the target device and the cooperation device. Alternatively, the network side
device instructs to establish the sidelink between the target device and the cooperation
device. If the network side device authorizes the target device to communicate with
the cooperation device on the sidelink, it may be considered that the sidelink is
established between the target device and the cooperation device.
[0039] In an embodiment, the cooperation group identifier is different from the target device
identifier and the cooperation device identifier. In another embodiment, the network
side device may further directly configure the target device identifier as the cooperation
group identifier. The cooperation group identifier is unique to at least one cell.
[0040] S101. The cooperation device receives the to-be-transmitted data sent by the network
side device to the cooperation group.
[0041] S102. The target device receives the to-be-transmitted data sent by the network side
device to the cooperation group.
[0042] When the network side device needs to send the to-be-transmitted data to the target
device, the network side device multicasts the to-be-transmitted data by using the
cooperation group identifier. The target device and each cooperation device parse
the to-be-transmitted data by using the cooperation group identifier.
[0043] It may be understood that there is no sequence of performing steps S101 and S102.
[0044] S103. The cooperation device sends the to-be-transmitted data to the target device
before a first moment.
[0045] A moment at which the target device feeds back, to the network side device, whether
the to-be-transmitted data (ACK/NACK) is correctly received is defined as the first
moment. A moment at which the cooperation device sends the to-be-transmitted data
to the target device is defined as a second moment. Duration between the second moment
and the first moment is greater than or equal to duration required by the target device
to receive, process, and check the to-be-transmitted data sent by the cooperation
device.
[0046] The receiving, processing, and checking may be understood as performing receiving,
parsing, decoding, checking, and the like on the to-be-transmitted data. After the
target device receives, processes, and checks the to-be-transmitted data sent by the
cooperation device, the target device may determine whether the to-be-transmitted
data sent by the cooperation device is successfully received.
[0047] S104. The target device receives, processes, and checks, before the first moment,
the to-be-transmitted data sent by the cooperation device.
[0048] Specifically, step S103 includes: The cooperation device sends the to-be-transmitted
data to the target device by using the sidelink between the cooperation device and
the target device. Step S104 includes: The target device receives, processes, and
checks, before the first moment by using the sidelink, the to-be-transmitted data
sent by the cooperation device. Sidelink communication is not constrained by network
coverage, and may work in a plurality of scenarios with network coverage, with no
network coverage, with partial network coverage, and the like.
[0049] In an existing LTE system, considering a processing delay, a transmission delay,
and the like of data decoding, a terminal usually requires three subframes to complete
receiving, processing, checking, and the like of downlink data. For the downlink data
received by the terminal in an N
th subframe, the terminal usually gives an uplink feedback in an (N+4)
th subframe, to notify the network side device whether the downlink data is correctly
received. If the downlink data is correctly received, the terminal feeds back an ACK.
If the downlink data is incorrectly received, the terminal feeds back a NACK to trigger
a base station to perform retransmission. Therefore, in the existing LTE system, if
the network side device sends the to-be-transmitted data to the cooperation group
in an N
th subframe, the cooperation device and the target device receive the to-be-transmitted
data in the N
th subframe, and the cooperation device and the target device require three subframes
to complete receiving, processing, checking, and the like of the to-be-transmitted
data. The target device needs to feed back, to the network side device in an (N+4)
th subframe, whether the to-be-transmitted data is correctly received. The cooperation
device does not have enough time to forward the to-be-transmitted data to the target
device before the (N+4)
th subframe. Alternatively, even if the cooperation device can forward the to-be-transmitted
data to the target device before the (N+4)
th subframe, the target device still does not have enough time to complete receiving,
processing, checking, and the like of the to-be-transmitted data forwarded by the
cooperation device. Therefore, in the prior art, the cooperation device cannot help
the network side device improve a success probability of initial data transmission.
In actual application, a probability that the target device feeds back a NACK to the
network side device for the first time is approximately 10%. A probability that the
target device feeds back a NACK to the network side device for the second time is
approximately 1‰. Therefore, it is very necessary to improve a success probability
of initial transmission performed by the network side device to the target device,
to obtain a greater gain.
[0050] In this embodiment of the present invention, the following implementations may be
used, so that the target device can have enough time (that is, before the first moment)
to receive, process, and check the to-be-transmitted data forwarded by the cooperation
device.
[0051] Implementation 1: In a faster cooperation mode (Faster Cooperation Mode, FCM), a
transmission time interval TTI used for transmission between the cooperation device
and the target device is less than a TTI used for transmission between the target
device and the network side device, in other words, the TTI used on the sidelink is
less than the TTI used for the transmission between the target device and the network
side device. A TTI is a time length required for independent decoding and transmission
in wireless communication. In the faster cooperation mode, cooperation transmission
can be quickly implemented without changing HARQ feedback duration and a HARQ process
of the target device for the to-be-transmitted data sent by the network side device
and without increasing a delay.
[0052] In this implementation, the transmission time interval used on the sidelink is defined
as a TTI 1, and the transmission time interval used for the transmission between the
target device and the network side device is defined as a TTI 2. The TTI 1 is less
than the TTI 2. There may be an algebraic relationship between the TTI 1 and the TTI
2, for example,
TTI 2 =
k ·
TTI 1, and k > 1. A specific value of k may be set based on an actual requirement, provided
that the target device can receive, process, and check, before the first moment, the
to-be-transmitted data sent by the cooperation device. As shown in FIG. 3, the TTI
used on the sidelink is a TTI (namely, the TTI 1) corresponding to an SL frame in
FIG. 3, and the TTI used for the transmission between the target device and the network
side device is a TTI (namely, the TTI 2) corresponding to a DL frame and a UL frame
in FIG. 3. The TTI 1 is less than the TTI 2. Therefore, in duration between a moment
at which the network side device sends the to-be-transmitted data and the first moment,
a quantity of TTIs 1 is greater than a quantity of TTIs 2.
[0053] In this embodiment of the present invention, a quantity of subframes required by
the target device and the cooperation device to receive, process, and check the to-be-transmitted
data may be, for example, 1, 2, or 3. A specific quantity of required subframes may
be set based on an actual requirement, and is not limited herein. Regardless of the
quantity of subframes required by the target device and the cooperation device to
receive, process, and check the to-be-transmitted data, the quantity of TTIs 1 in
the duration between the moment at which the network side device sends the to-be-transmitted
data and the first moment only needs to be enough for the cooperation device to receive
and forward the to-be-transmitted data, and enough for the target device to receive,
process, and check the to-be-transmitted data forwarded by the cooperation device.
[0054] The TTI 1 may be enabled to be less than the TTI 2 in the following manners.
[0055] Manner 1: A quantity of symbols included in a subframe corresponding to the TTI 1
is less than a quantity of symbols included in a subframe corresponding to the TTI
2.
[0056] A smaller quantity of symbols in a subframe indicates a shorter subframe length and
a shorter corresponding TTI.
[0057] Manner 2: A length of the symbol included in the subframe corresponding to the TTI
1 is less than a length of the symbol included in the subframe corresponding to the
TTI 2.
[0058] A length of a symbol depends on a size of a subcarrier spacing, and a greater subcarrier
spacing indicates a shorter symbol length. Therefore, a subcarrier spacing used on
the sidelink is greater than a subcarrier spacing used for the transmission between
the target device and the network side device.
[0059] As shown in FIG. 3, it is assumed that the network side device sends to-be-transmitted
data to the cooperation group in an N
th subframe (namely, a DL frame N in FIG. 3), and the cooperation device and the target
device receive the to-be-transmitted data in the N
th subframe. After making preparations to parse and send the received to-be-transmitted
data, the cooperation device forwards the to-be-transmitted data to the target device
in an M
th sidelink subframe (namely, an SL frame M in FIG. 3). It is assumed that the target
device requires three sidelink subframes to complete receiving, processing, checking,
and the like of the to-be-transmitted data, and it is assumed that the target device
feeds back, to the network side device in a UL frame N+4, whether the to-be-transmitted
data is correctly received. Therefore, it only needs to be ensured that an (M+3)
th sidelink subframe is before the UL frame N+4.
[0060] The manner 1 and the manner 2 may be used in combination.
[0061] Implementation 2: In a longer cooperation mode (Longer Cooperation Mode, LCM), a
moment at which the target device receives the to-be-transmitted data sent by the
network side device is defined as a third moment. Duration between the third moment
and the first moment is greater than duration required by the target device to receive,
process, and check the to-be-transmitted data sent by the network side device. The
target device has at least one subframe that is between the third moment and the first
moment and that is not used to process the to-be-transmitted data sent by the network
side device, so that the target device has enough time to receive, process, and check
the to-be-transmitted data forwarded by the cooperation device. In the longer cooperation
mode, cooperation transmission can be implemented without changing the TTI used for
the transmission between the cooperation device and the target device on the sidelink
and without increasing processing complexity.
[0062] As shown in FIG. 4, it is assumed that the transmission time interval used on the
sidelink is equal to the transmission time interval used for the transmission between
the network side device and the cooperation group. The network side device sends to-be-transmitted
data to the cooperation group in an N
th subframe. After the target device receives, in the N
th subframe, the to-be-transmitted data sent by the network side device, and processes
the to-be-transmitted data sent by the network side device by using three subframes,
four idle subframes are reserved, and an ACK/a NACK is fed back to the network side
device in an (N+8)
th subframe. The cooperation device receives the to-be-transmitted data in the N
th subframe, the cooperation device requires three subframes to process the to-be-transmitted
data, and the cooperation device forwards the to-be-transmitted data to the target
device in an (N+4)
th subframe. The target device also requires three subframes to process the to-be-transmitted
data forwarded by the cooperation device, and the target device processes the to-be-transmitted
data in an (N+7)
th subframe, in other words, the target device may receive, process, and check, before
the (N+8)
th subframe, the to-be-transmitted data sent by the target device.
[0063] The implementation 1 and the implementation 2 may be used in combination.
[0064] In a same cooperation group, all cooperation devices and target devices may complete
a cooperation process only by using a same cooperation policy. The cooperation policy
includes a used cooperation mode and parameters specifically used in the cooperation
mode. The cooperation mode includes the faster cooperation mode, the longer cooperation
mode, or a manner of combining the two modes. The parameters used in the cooperation
mode include a parameter used for the sidelink and HARQ feedback duration of the target
device for the to-be-transmitted data sent by the network side device. The parameter
used for the sidelink includes at least one of a transmission time interval, a quantity
of symbols included in each subframe, a subcarrier spacing corresponding to the symbol,
a frequency band (channel) used for the sidelink, and a time-frequency resource used
for the sidelink. The HARQ feedback duration of the target device for the to-be-transmitted
data sent by the network side device is duration between a moment at which the target
device receives the to-be-transmitted data sent by the network side device and a moment
at which the target device feeds back, to the network side device, whether the to-be-transmitted
data is correctly received.
[0065] In an embodiment, the network side device may send cooperation control signaling
to the cooperation device and the target device, and the cooperation control signaling
indicates the cooperation policy. Alternatively, the network side device may send
cooperation control signaling to the target device, and the target device forwards
the cooperation control signaling to the cooperation device. The cooperation control
signaling delivered by the network side device may be carried in downlink control
information of a physical downlink control channel (Physical Downlink Control Channel,
PDCCH), or carried in radio resource control (Radio Resource Control, RRC) signaling,
or carried in a system information block (System Information Block, SIB). Unified
management may be implemented by using the network side device to indicate, thereby
effectively avoiding interference between terminal devices.
[0066] It may be understood that when the cooperation control signaling indicates the cooperation
policy, it may not be necessary to separately indicate the cooperation mode. A specific
cooperation mode to be used may be directly represented by using a parameter specifically
used in the cooperation mode.
[0067] In an embodiment, the cooperation control signaling may directly indicate the parameter
specifically used in the cooperation mode.
[0068] In another embodiment, the cooperation control signaling may indicate a sequence
number corresponding to the cooperation policy. The cooperation device and the target
device may prestore a table of a correspondence between the cooperation policy and
the sequence number. After the cooperation device and the target device obtain the
sequence number corresponding to the cooperation policy, the cooperation policy indicated
by the cooperation control signaling may be obtained by directly searching the table,
thereby reducing overheads of the cooperation control signaling.
[0069] The table of the correspondence may use a presentation form shown in Table 1. A value
of HARQ feedback duration X of the target device is taken as X1, X2 to Xn respectively,
and n represents a quantity of values of X. For example, n=5, X1=1, X2=2, X3=4, X4=8,
and X5=16. HARQ feedback duration X of the target device indicates: If the target
device receives, in an N
th frame, to-be-transmitted data sent by the network side device, the target device
feeds back an ACK/a NACK to the network side device in an (N+X)
th frame. A value of a quantity of symbols included in each TTI 1 may be taken as 1,
2 to M respectively. Sequence numbers corresponding to different parameter combinations
may be calculated directly based on a preset algebraic relational expression. In Table
1, a maximum of 350 different parameter combinations are supported, which are corresponding
to 350 sequence numbers.
Table 1
|
Subcarrier spacing k [KHz] |
15 |
30 |
60 |
120 |
240 |
HARQ feedback duration |
X1 |
Quantity of symbols corresponding to one TTI 1 |
1 |
Index= 1 |
Index = M x n + 1 |
. |
. |
Index = 4 x M x n + 1 |
|
|
|
2 |
Index=2 |
Index = M x n +2 |
. |
. |
Index = 4 x M x n + 2 |
|
|
|
3 |
Index=3 |
Index = M x n +3 |
. |
. |
Index = 4 x M x n + 3 |
|
|
|
. |
. |
. |
. |
. |
. |
|
|
|
M |
Index=M |
Index = M x n +M |
. |
. |
Index = 4 x M x n+M |
|
... |
... |
... |
|
Xn |
Quantity of symbols corresponding to one TTI 1 |
1 |
Index = M x (n - 1) + 1 |
Index = M x n + M x (n- 1) + 1 |
. |
. |
Index = 4 x M x n + M x (n - 1) + 1 |
|
|
|
2 |
Index = M x (n - 1) + 2 |
Index = M x n + M x (n - 1) + 2 |
. |
. |
Index = 4 x M x n + M x (n - 1) +2 |
|
|
|
3 |
Index = M x (n - 1) + 3 |
Index = M x n + M x (n - 1)+ 2 |
. |
. |
Index = 4 x M x n + M x (n - 1) + 3 |
|
|
|
. |
. |
. |
. |
. |
. |
|
|
|
M |
Index = M x n |
Index = 2 x M x n |
. |
. |
Index = 5 x M x n |
[0070] The table of the correspondence may use a presentation form shown in Table 2. That
is, each sequence number corresponds to one parameter combination, and the parameter
combination specifically includes a subcarrier spacing, HARQ feedback duration X,
and a quantity of symbols included in each TTI 1. The sequence number may be indicated
by using nine bits. For example, "000 000 000" indicates a sequence number equals
to 1, and "000 000 010" indicates a sequence number equals to 3.
Table 2
|
|
|
|
Subcarrier spacing k [KHz] |
|
|
|
|
|
|
15 |
30 |
60 |
120 |
240 |
HARQ feedback duration |
1 |
Quantity of symbols corresponding to one TTI 1 |
1 |
index= 1 |
index=71 |
index=141 |
index=211 |
index=281 |
2 |
index=2 |
index=72 |
index=142 |
index=212 |
index=282 |
... |
14 |
index=14 |
index=84 |
index=154 |
index=224 |
index=294 |
2 |
Quantity of symbols corresponding to one TTI 1 |
1 |
index= 15 |
index=85 |
index=155 |
index=225 |
index=295 |
2 |
index=16 |
index=86 |
index=156 |
index=226 |
index=296 |
... |
14 |
index=28 |
index=98 |
index=168 |
index=238 |
index=308 |
... |
... |
... |
16 |
Quantity of symbols corresponding to one TTI 1 |
1 |
index=57 |
index=127 |
index= 197 |
index=267 |
index=337 |
2 |
index=58 |
index=128 |
index= 198 |
index=268 |
index=338 |
... |
14 |
index=70 |
index=140 |
index=210 |
index=280 |
index=350 |
[0071] The table of the correspondence may use a presentation form shown in Table 3. That
is, each sequence number corresponds to one parameter combination, and the parameter
combination specifically includes a subcarrier spacing, HARQ feedback duration X,
and a quantity of symbols included in each TTI 1. A value of HARQ feedback duration
X of the target device is taken as X1, X2 to Xn respectively, and n represents a quantity
of values of X. For example, n=5, X1=1, X2=2, X3=4, X4=8, and X5=16. A value of a
quantity of symbols included in each TTI 1 may be taken as 1, 2 to M respectively.
In the presentation form shown in Table 3, it is easier for the cooperation device
and the target device to find corresponding parameters based on the sequence numbers
indicated by the cooperation control signaling.
Table 3
Index |
Parameter |
1 |
Subcarrier spacing=15 KHz; X=X1; and quantity of symbols corresponding to one TTI
1=1. |
. |
. |
M x n |
Subcarrier spacing=15 KHz; X=Xn; and quantity of symbols corresponding to one TTI
1=M. |
. |
. |
2 x M x n |
Subcarrier spacing=30 KHz; X=Xn; and quantity of symbols corresponding to one TTI
1=M. |
. |
. |
3 x M x n |
Subcarrier spacing=60 KHz; X=Xn; and quantity of symbols corresponding to one TTI
1=M. |
. |
. |
4 x M x n |
Subcarrier spacing=120 KHz; X=Xn; and quantity of symbols corresponding to one TTI
1=M. |
. |
. |
5 x M x n |
subcarrier spacing=240 KHz; X=Xn; and quantity of symbols corresponding to one TTI
1=M. |
[0072] It may be understood that, meanings represented in Table 1, Table 2, and Table 3
are the same, and only different expression forms are used.
[0073] It may be understood that values of X and M in Table 1, Table 2, and Table 3 may
be any non-negative integer. Table 1 merely provides an example, and is not enumerated
one by one. The subcarrier spacing in Table 1 is respectively 15 KHz, 30 KHz, 60 KHz,
120 KHz, and 240 KHz. This is also merely an example. The present invention is still
applicable to another subcarrier spacing such as 7.5 KHz or 480 KHz.
[0074] In another embodiment, the cooperation device determines the cooperation policy based
on a rule agreed with the target device. Likewise, the target device also determines
the cooperation policy based on the rule agreed with the cooperation device. The cooperation
device and the target device separately determine the cooperation policy, so that
a signaling indication of the network side device is reduced, control channel overheads
are effectively reduced, and the like. A specific rule is set, so that the cooperation
device and the target device can determine a same cooperation policy. In this embodiment,
the cooperation device and the target device may not need an explicit indication of
the network side device, but actively determine, based on a specific rule, a parameter
combination that should be used to cooperate. For example, for the faster cooperation
mode, the rule may be, for example: Time required for completing data transmission
is calculated based on at least one parameter of a size of a data buffer (Buffer),
an MCS (Modulation and Coding Scheme, modulation and coding scheme) configuration,
bandwidth information, and the like, and then the TTI 1 that can be used to meet the
time is determined. For example, with bandwidth support, a maximum TTI 1 that is determined
based on the size of the data buffer and the MCS configuration and that the TTI 1
is less than the TTI 2. It may be understood that, it is only needs to be ensured
that the TTI 1 is less than the TTI 2. Excessively small TTI 1 increases hardware
processing complexity and causes a waste of resources. The rule should be consistent
for all cooperation devices and target devices, for example, it may be expressed in
a standard. Similarly, for the longer cooperation mode and a manner of combining the
two modes, parameters used by the cooperation policy may also be determined based
on at least one of the size of the data buffer (Buffer), the MCS (Modulation and Coding
Scheme, modulation and coding scheme) configuration, the bandwidth information, and
the like, it is only needs to be ensured that the determined parameters are unique.
[0075] S105. The target device feeds back, to the network side device at the first moment,
whether the to-be-transmitted data is correctly received. In other words, the target
device feeds back an ACK/a NACK to the network side device.
[0076] Before the first moment, the target device can receive, process, and check the to-be-transmitted
data sent by the network side device, and can receive, process, and check the to-be-transmitted
data forwarded by the cooperation device. Therefore, even if the target device cannot
correctly receive the to-be-transmitted data sent by the network side device, if the
target device can correctly receive the to-be-transmitted data forwarded by the cooperation
device, the target device does not need to request the network side device to retransmit
the to-be-transmitted data. In this embodiment of the present invention, the cooperation
device assists the network side device to send data to the target device, which can
effectively improve a success probability that the target device receives data, and
reduce a probability that the network side device performs retransmission to the target
device.
[0077] Further, in an embodiment, a frequency band used on the foregoing sidelink for data
transmission may be a licensed frequency band. It should be understood that, a conventional
licensed spectrum resource is a spectrum resource that can be used only when a national
or a local radio committee is approved. Different systems (for example, an LTE system
and a WiFi system) or systems of different operators cannot share a licensed spectrum
resource. The licensed frequency band and a frequency band allocated by the network
side device to the target device or the cooperation device have at least partial overlap.
[0078] In another embodiment, a frequency band used on the foregoing sidelink for data transmission
may be an unlicensed frequency band. It should be understood that conventional unlicensed
frequency band transmission means that no system allocation is required, and communications
devices may share resources included in the unlicensed frequency band. Resource sharing
on the unlicensed frequency band means that only limitations on indexes such as transmit
power and out-of-band leakage are specified for use of a specific frequency spectrum,
to ensure that a basic coexistence requirement is met between a plurality of devices
that jointly use the frequency band. An operator may implement network capacity offloading
by using the unlicensed frequency band resource, but needs to obey regulations and
requirements formulated by different regions and different spectrums for the unlicensed
frequency band resource. These requirements are usually posed to protect a public
system such as radar and to ensure that a plurality of systems fairly coexist and
cause as little negative impact to each other as possible, and include a transmit
power limit, an out-of-band emission indicator, indoor and outdoor use restrictions.
In addition, some regions further have some additional coexistence policies and the
like. The unlicensed frequency band has low use costs, does not cause interference
to communication between the network side device and the target device or the cooperation
device, and does not occupy a valuable licensed frequency band resource.
[0079] In the following embodiments, for example, the unlicensed frequency band is used.
Each terminal device may use the unlicensed frequency band in a contention manner
or a sensing manner. For example, the terminal device uses the unlicensed spectrum
resource in a listen before talk (LBT, Listen Before Talk) manner. In other words,
before the terminal device sends data, at least one channel on the unlicensed frequency
band is first sensed. For example, the sensing manner may be Cat-4, Cat-2, or the
like. The channel can be occupied to send the to-be-transmitted data to the target
device only when a sensing result is idle. Otherwise, the channel cannot be used.
[0080] In an embodiment, a channel used for transmission on the sidelink includes one or
more candidate sidelink channels. These candidate sidelink channels may be pre-specified.
The cooperation device may select, based on an indication of the network side device,
or an indication of the target device, or a preset rule, or randomly select a channel
from one or more candidate sidelink channels to sense.
[0081] In an embodiment, step S104 specifically includes: The target device separately senses
on each candidate sidelink channel, the to-be-transmitted data sent by the cooperation
device. Therefore, the target device may receive, as much as possible, the to-be-transmitted
data sent by the cooperation device, which may further improve a probability that
the target device correctly receives the to-be-transmitted data.
[0082] Different sidelink channels may have different availability. For example, sensing
duration of cooperation device CUE 1 may be a length of two sidelink subframes, sensing
duration of cooperation device CUE 2 may be a length of one sidelink subframe, and
sensing duration of cooperation devices CUE 3 and CUE 4 may be a length of three sidelink
subframes. Therefore, each cooperation device cannot send the to-be-transmitted data
to the target device in a same sidelink subframe. If the target device can correctly
receive the to-be-transmitted data that is first sent by each cooperation device,
or the target device can correctly receive the to-be-transmitted data sent by the
network side device, the target device does not need to continue to wait for receiving
the to-be-transmitted data that is not sent by each cooperation device. Cooperation
devices that do not send the to-be-transmitted data do not need to send the to-be-transmitted
data to a target device, to reduce a spectrum resource and energy consumption. To
resolve this problem, in an embodiment, the target device may send, to the cooperation
device, information (ACK/NACK) used to indicate whether the to-be-transmitted data
is correctly received. Therefore, when receiving an ACK fed back by the target device,
the cooperation device does not need to send the to-be-transmitted data to the target
device, thereby effectively reducing the spectrum resource. Further, as shown in FIG.
5, the method further includes the following steps.
[0083] S106. The target device sends, in a common sidelink subframe (Common SL Subframe),
information used to indicate whether the to-be-transmitted data is correctly received.
The common sidelink subframe is a subframe at a preset location that is on the sidelink
channel and that is agreed on between the target device and the cooperation device.
[0084] The subframe at the preset location may be understood as a subframe corresponding
to a preset subframe number. For example, an (M+2)
th frame, an (M+8)
th frame, or an (M+14)
th frame.
[0085] In an embodiment, before sending an ACK/a NACK in the common sidelink subframe, the
target device may first sense on each sidelink channel, and then send an ACK/a NACK
on common sidelink subframes on all available channels.
[0086] In an embodiment, locations of common sidelink subframes on the sidelink channels
may be the same. In other words, the target device may separately send an ACK/a NACK
on the all available sidelink channels at a same moment (namely, a moment corresponding
to the common sidelink subframe). As shown in FIG. 6A, FIG. 6B, FIG. 6C, and FIG.
6D, a location of one common sidelink subframe is M+2, and the target device sends
an ACK/a NACK in an (M+2)
th sidelink subframe on all sidelink channels. In another embodiment, locations of common
sidelink subframes on the sidelink channels may also be different.
[0087] In another embodiment, the common sidelink subframe may also be set on some sidelink
channels. The target device and the cooperation device negotiate to set a channel
on which the common sidelink subframe is located and a location of the common sidelink
subframe, so that the cooperation device receives an ACK/a NACK in the common sidelink
subframe on corresponding channel.
[0088] A common sidelink subframe on each sidelink channel forms a common ACK pool (Common
ACK Pool). Indication information of the common ACK pool may be configured by the
network side device, may be determined through negotiation between the target device
and the cooperation device, or may be predetermined in a standard.
[0089] S107. The cooperation device receives, in the common sidelink subframe, information
used to indicate whether the target device correctly receives the to-be-transmitted
data.
[0090] When a sidelink subframe before the common sidelink subframe ends, if the cooperation
device does not complete a sensing process, or just completes the sensing process
but has not yet sent the to-be-transmitted data to the target, the cooperation device
stops a current action, keeps a receiving state when the common sidelink subframe
arrives, and receives an ACK/a NACK fed back by the target device.
[0091] If the cooperation device receives, before completing sending of the to-be-transmitted
data to the target device, information used to indicate that the target device correctly
receives the to-be-transmitted data, the cooperation device abandons sending the to-be-transmitted
data to the target device.
[0092] In this embodiment, if the cooperation device does not complete the sensing process
or just completes the sensing process but has not yet sent the to-be-transmitted data
to the target device, it is considered that the cooperation device has not send the
to-be-transmitted data to the target device.
[0093] If the cooperation device receives, in the common sidelink subframe, ACK information
fed back by the target device, it indicates that the target device correctly receives
the to-be-transmitted data. After the common sidelink subframe, the cooperation device
may abandon sending the to-be-transmitted data to the target device. It may be understood
that, the cooperation device stops a sensing process that has not been completed,
which may also be considered that the cooperation device abandons sending the to-be-transmitted
data to the target device.
[0094] In another embodiment, if the cooperation device receives, in the common sidelink
subframe, NACK information fed back by the target device, it indicates that the target
device does not correctly receive the to-be-transmitted data. After the common sidelink
subframe, the cooperation device continues the sensing process that has not been completed.
Alternatively, the cooperation device continues sending the to-be-transmitted data
to the target device.
[0095] In another embodiment, if the cooperation device receives, in the common sidelink
subframe after sending the to-be-transmitted data to the target device, NACK information
fed back by the target device, it indicates that the target device does not correctly
receive the to-be-transmitted data, and the cooperation device may resend the to-be-transmitted
data to the target device, to further improve a probability that the target device
correctly receives the to-be-transmitted data.
[0096] Further, in an embodiment, the cooperation device senses the sidelink channel, and
when senses an available sidelink channel, determines whether duration between a current
moment and a moment corresponding to a next common sidelink subframe is greater than
or equal to duration required for sending the to-be-transmitted data. When the duration
between the current moment and the moment corresponding to the next common sidelink
subframe is greater than or equal to the duration required for sending the to-be-transmitted
data, perform step S103. When the duration between the current moment and the moment
corresponding to the next common sidelink subframe is less than the duration required
for sending the to-be-transmitted data, before the next common sidelink subframe,
the cooperation device abandons sending the to-be-transmitted data to the target device,
and after the next common sidelink subframe, performs step S103. In this embodiment,
if the cooperation device completes the sensing process in one or more sidelink subframes
before the next common sidelink subframe, but if a quantity of remaining sidelink
subframes before the next common sidelink subframe is less than a quantity of subframes
required for sending the to-be-transmitted data, the cooperation device abandons sending
the to-be-transmitted data to the target device, and sends the to-be-transmitted data
to the target device after the next common sidelink subframe.
[0097] In an embodiment, the cooperation device may start a sensing process before receiving
the to-be-transmitted data sent by the network side device, or start the sensing process
immediately after receiving the to-be-transmitted data, to send the to-be-transmitted
data to the target device as soon as possible. As shown in FIG. 6A, FIG. 6B, FIG.
6C, and FIG. 6D, CUE 1 completes sensing in an M
th sidelink subframe, and CUE 2 completes sensing before the M
th sidelink subframe. It may be determined, by calculation, that the to-be-transmitted
data may be sent by using one sidelink subframe. Therefore, CUE 1 and CUE 2 send the
to-be-transmitted data to the target device in an (M+1)
th sidelink subframe, and receive a feedback of TUE in an (M+2)
th sidelink subframe (namely, the common sidelink subframe). Because an LBT process
is still not completed in the (M+1)
th sidelink subframe, the CUE 3 and the CUE 4 stop a current process, and receive the
feedback of TUE in the (M+2)
th sidelink subframe (namely, the common sidelink subframe). If the feedback is a NACK,
the sensing process continues in an (M+3)
th sidelink subframe.
[0098] Further, the cooperation device selects channel based on an instruction of the target
device instead of based on an instruction of the network side device.
[0099] Specifically, in an embodiment, the target device may start the sensing process before
receiving the to-be-transmitted data sent by the network side device, or start the
sensing process immediately after receiving the to-be-transmitted data, and send sidelink
common control information (Sidelink Common Control Information, SCCI) on all available
sidelink channels after sensing is completed.
[0100] SCCI includes scheduling information of the cooperation device, in other words, parameter
information such as resource indication information and MCS that are of each cooperation
device on the sidelink, and resource indication information that the target device
feeds back an ACK/a NACK on the sidelink, and the like. SCCI may further include 1-bit
cooperation indication information, and the cooperation indication information is
used to notify the cooperation device whether cooperation transmission needs to be
performed.
[0101] The cooperation device receives SCCI, and sends, based on an instruction of SCCI,
the to-be-transmitted data to the target device on a resource specified by the target
device for the cooperation device and based on parameters such as a specified MCS.
Before sending the to-be-transmitted data, the cooperation device may perform sensing,
and sends the to-be-transmitted data after the sensing is completed.
[0102] The target device receives, at the resource location specified by SCCI, the to-be-transmitted
data sent by the cooperation device, and sends, at the resource location specified
by SCCI, an ACK/a NACK to the cooperation device. The target device may perform sensing
before sending an ACK/a NACK, and sends an ACK/a NACK after the sensing is completed.
Alternatively, the target device may directly send an ACK/a NACK without sensing.
[0103] The cooperation device receives, at the resource location specified by the SCCI,
an ACK/a NACK sent by the target device.
[0104] As shown in FIG. 7A, FIG 7B, FIG. 7C, and FIG. 7D, if the target device completes
sensing before an M
th sidelink subframe, the target device may send SCCI to all cooperation devices in
the M
th subframe of each available sidelink channel. After receiving SCCI, the cooperation
devices CUE 1, CUE 2, CUE 3, and CUE 4 separately start to sense, based on an instruction
of SCCI, on corresponding sidelink channels, and send, after the sensing succeeds,
the to-be-transmitted data to the target device on the resource location specified
by SCCI. After receiving the to-be-transmitted data, the target device feeds back
an ACK/a NACK. CUE 1, CUE 2, CUE 3, and CUE 4 receive an ACK/ a NACK feedback of the
target device at the specified location based on the instruction of SCCI.
[0105] It may be understood that, in the foregoing embodiments, a cooperation device of
one cooperation group may also be a cooperation device of another cooperation group,
in other words, one cooperation device may perform cooperation transmission for a
plurality of cooperation groups at the same time.
[0106] The present invention further provides a communications device 100. The communications
device 100 may be the cooperation device described in the foregoing embodiments. As
shown in FIG. 8, the communications device 100 includes a transceiver 110 and a processor
120. The transceiver 110 is connected to the processor 120. Optionally, the communications
device 100 further includes a memory 130. The memory 130 is separately connected to
the processor 120 and the transceiver 110. Further, optionally, the communications
device 100 further includes a bus system 140. The processor 120, the transceiver 110,
and the memory 130 may be connected by using the bus system 140. The memory 140 may
be configured to store an instruction, and the processor 120 is configured to execute
the instruction stored in the memory 140, to control the transceiver 110 to receive
and send a signal. The memory 140 may be further configured to cache data generated
when the processor 120 executes the instruction.
[0107] The transceiver 110 is configured to receive to-be-transmitted data sent by a network
side device to a cooperation group, where the cooperation group includes the communications
device 100 and a target device.
[0108] The processor 120 is configured to control the transceiver 110 to send the to-be-transmitted
data to the target device before a first moment. A moment at which the target device
feeds back, to the network side device, whether the to-be-transmitted data is correctly
received is defined as the first moment. A moment at which the transceiver 110 sends
the to-be-transmitted data to the target device is defined as a second moment. Duration
between the second moment and the first moment is greater than or equal to duration
required by the target device to receive, process, and check the to-be-transmitted
data sent by the transceiver.
[0109] It can be learned from the foregoing embodiment that the communications device 100
shown in FIG. 7A, FIG. 7B, FIG. 7C, and FIG. 7D performs steps S101, S103, and S107
in the embodiment shown in FIG. 5. For more details when the transceiver 110 and the
processor 120 perform the foregoing steps, refer to related descriptions in the embodiments
shown in FIG. 2 and FIG. 5. Details are not described herein again.
[0110] In this embodiment of the present invention, even if the target device cannot correctly
receive the to-be-transmitted data sent by the network side device, if the target
device can correctly receive the to-be-transmitted data forwarded by the communications
device 100, the target device does not need to request the network side device to
retransmit the to-be-transmitted data, which can effectively improve a success probability
that the target device receives data, and reduce a probability that the network side
device performs retransmission to the target device.
[0111] For other functions of the processor 120 and the transceiver 110, refer to descriptions
of corresponding embodiments in the foregoing data transmission method. Details are
not described herein again.
[0112] The present invention further provides a communications device 200. The communications
device 200 may be the target device described in the foregoing embodiments. As shown
in FIG. 9, the communications device 200 includes a transceiver 210 and a processor
220. The transceiver 210 is connected to the processor 220. Optionally, the communications
device 200 further includes a memory 230. The memory 230 is separately connected to
the processor 220 and the transceiver 210. Further, optionally, the communications
device 200 further includes a bus system 240. The processor 220, the transceiver 210,
and the memory 230 may be connected by using the bus system 240. The memory 240 may
be configured to store an instruction, and the processor 220 is configured to execute
the instruction stored in the memory 240, to control the transceiver 210 to receive
and send a signal. The memory 240 may be further configured to cache data generated
when the processor 220 executes the instruction.
[0113] The transceiver 210 is configured to receive to-be-transmitted data sent by a network
side device to a cooperation group, where the cooperation group includes a cooperation
device and the communications device.
[0114] The transceiver 210 is further configured to receive the to-be-transmitted data sent
by the cooperation device.
[0115] The processor 220 is configured to process and check, before a first moment, the
to-be-transmitted data sent by the cooperation device. A moment at which the communications
device 200 feeds back, to the network side device, whether the to-be-transmitted data
is correctly received is defined as the first moment.
[0116] It can be learned from the foregoing embodiment that the communications device 200
shown in FIG. 8 performs steps S102, S104, S105 and S106 in the embodiment shown in
FIG. 5. For more details when the transceiver 110 and the processor 120 perform the
foregoing steps, refer to related descriptions in the embodiments shown in FIG. 2
and FIG. 5. Details are not described herein again.
[0117] In this embodiment of the present invention, even if the communications device 200
cannot correctly receive the to-be-transmitted data sent by the network side device,
if the communications device 200 can correctly receive the to-be-transmitted data
forwarded by the cooperation device, the communications device 200 does not need to
request the network side device to retransmit the to-be-transmitted data, which can
effectively improve a success probability that the communications device 200 receives
data, and reduce a probability that the network side device performs retransmission
to the communications device 200.
[0118] For other functions of the processor 120 and the transceiver 110, refer to descriptions
of corresponding embodiments in the foregoing data transmission method. Details are
not described herein again.
[0119] The present invention further provides a data transmission system. The data transmission
system includes the communications device 100 and the communications device 200 described
in the foregoing embodiments. For details, refer to the foregoing embodiments. Details
are not described herein again.
[0120] A person of ordinary skill in the art may understand that all or some of the steps
of the foregoing methods may be implemented by a program instructing relevant hardware.
The program may be stored in a computer-readable storage medium. The storage medium
includes: a ROM, a RAM, and an optical disc.
[0121] To sum up, the foregoing descriptions are merely embodiments of the present invention,
but are not intended to limit the protection scope of the present invention. Any modification,
equivalent replacement, or improvement made without departing from the spirit and
principle of the present invention shall fall within the protection scope of the present
invention.
1. A data transmission method, wherein the method comprises:
receiving, by a cooperation device, to-be-transmitted data sent by a network side
device to a cooperation group, wherein the cooperation group comprises the cooperation
device and a target device; and
sending, by the cooperation device, the to-be-transmitted data to the target device
before a first moment, wherein
a moment at which the target device feeds back, to the network side device, whether
the to-be-transmitted data is correctly received is defined as the first moment, a
moment at which the cooperation device sends the to-be-transmitted data to the target
device is defined as a second moment, and duration between the second moment and the
first moment is greater than or equal to duration required by the target device to
receive, process, and check the to-be-transmitted data sent by the cooperation device.
2. The method according to claim 1, wherein a transmission time interval TTI used for
transmission between the cooperation device and the target device is less than a TTI
used for transmission between the target device and the network side device.
3. The method according to claim 1 or 2, wherein the sending, by the cooperation device,
the to-be-transmitted data to the target device comprises: sending, by the cooperation
device, the to-be-transmitted data to the target device by using a sidelink between
the cooperation device and the target device.
4. The method according to claim 3, wherein a frequency band used for transmission on
the sidelink is a licensed frequency band or an unlicensed frequency band.
5. The method according to claim 4, wherein when the unlicensed frequency band is used
for transmission on the sidelink, a channel used for transmission on the sidelink
comprises one or more candidate sidelink channels, and the method further comprises:
receiving, by the cooperation device in a common sidelink subframe, information used
to indicate whether the target device correctly receives the to-be-transmitted data,
wherein the common sidelink subframe is a subframe at a preset location that is on
the sidelink channel and that is agreed on between the target device and the cooperation
device.
6. The method according to claim 5, wherein the method further comprises:
if the cooperation device receives, before completing sending of the to-be-transmitted
data to the target device, information used to indicate that the target device correctly
receives the to-be-transmitted data, abandoning, by the cooperation device, sending
the to-be-transmitted data to the target device.
7. A data transmission method, wherein the method comprises:
receiving, by a target device, to-be-transmitted data sent by a network side device
to a cooperation group, wherein the cooperation group comprises a cooperation device
and the target device; and
receiving, processing, and checking, by the target device before a first moment, the
to-be-transmitted data sent by the cooperation device, wherein
a moment at which the target device feeds back, to the network side device, whether
the to-be-transmitted data is correctly received is defined as the first moment.
8. The method according to claim 7, wherein a transmission time interval TTI used for
transmission between the cooperation device and the target device is less than a TTI
used for transmission between the target device and the network side device.
9. The method according to claim 7 or 8, wherein a moment at which the target device
receives the to-be-transmitted data sent by the network side device is defined as
a third moment, and the target device has at least one subframe that is between the
third moment and the first moment and that is not used to process the to-be-transmitted
data sent by the network side device.
10. The method according to any one of claims 7 to 9, wherein the target device receives,
by using a sidelink between the target device and the cooperation device, the to-be-transmitted
data sent by the cooperation device.
11. The method according to claim 10, wherein a frequency band used for transmission on
the sidelink is a licensed frequency band or an unlicensed frequency band.
12. The method according to claim 11, wherein when the unlicensed frequency band is used
for transmission on the sidelink, a channel used for transmission on the sidelink
comprises one or more candidate sidelink channels, and the method further comprises:
sending, by the target device in a common sidelink subframe, information used to indicate
whether the to-be-transmitted data is correctly received, wherein the common sidelink
subframe is a subframe at a preset location that is on the sidelink channel and that
is agreed on between the target device and the cooperation device.
13. A communications device, wherein the communications device comprises a processor and
a transceiver;
the transceiver is configured to receive to-be-transmitted data sent by a network
side device to a cooperation group, wherein the cooperation group comprises the communications
device and a target device; and
the processor is configured to control the transceiver to send the to-be-transmitted
data to the target device before a first moment, wherein
a moment at which the target device feeds back, to the network side device, whether
the to-be-transmitted data is correctly received is defined as the first moment, a
moment at which the transceiver sends the to-be-transmitted data to the target device
is defined as a second moment, and duration between the second moment and the first
moment is greater than or equal to duration required by the target device to receive,
process, and check the to-be-transmitted data sent by the transceiver.
14. The communications device according to claim 13, wherein a transmission time interval
TTI used for transmission between the communications device and the target device
is less than a TTI used for transmission between the target device and the network
side device.
15. The communications device according to claim 13 or 14, wherein the processor is further
configured to control the transceiver to send the to-be-transmitted data to the target
device by using a sidelink between the transceiver and the target device.
16. The communications device according to claim 15, wherein a frequency band used for
transmission on the sidelink is a licensed frequency band or an unlicensed frequency
band.
17. The communications device according to claim 16, wherein when the unlicensed frequency
band is used for transmission on the sidelink, a channel used for transmission on
the sidelink comprises one or more candidate sidelink channels, and the transceiver
is further configured to receive, in a common sidelink subframe, information used
to indicate whether the target device correctly receives the to-be-transmitted data,
wherein the common sidelink subframe is a subframe at a preset location that is on
the sidelink channel and that is agreed on between the target device and the communications
device.
18. The communications device according to claim 17, wherein the transceiver is further
configured to receive information used to indicate that the target device correctly
receives the to-be-transmitted data, and if the transceiver receives, before completing
sending of the to-be-transmitted data to the target device, the information used to
indicate that the target device correctly receives the to-be-transmitted data, the
processor is further configured to control the transceiver to abandon sending the
to-be-transmitted data to the target device.
19. A communications device, wherein the communications device comprises a processor and
a transceiver;
the transceiver is configured to receive to-be-transmitted data sent by a network
side device to a cooperation group, wherein the cooperation group comprises a cooperation
device and the communications device;
the transceiver is further configured to receive the to-be-transmitted data sent by
the cooperation device; and
the processor is configured to process and check, before a first moment, the to-be-transmitted
data sent by the cooperation device, wherein
a moment at which the communications device feeds back, to the network side device,
whether the to-be-transmitted data is correctly received is defined as the first moment.
20. The communications device according to claim 19, wherein a transmission time interval
TTI used for transmission between the cooperation device and the communications device
is less than a TTI used for transmission between the communications device and the
network side device.
21. The communications device according to claim 19 or 20, wherein a moment at which the
transceiver receives the to-be-transmitted data sent by the network side device is
defined as a third moment, and the processor has at least one subframe that is not
used to process the to-be-transmitted data sent by the network side device and that
is between the third moment and the first moment.
22. The communications device according to any one of claims 19 to 21, wherein the transceiver
receives, by using a sidelink between the transceiver and the cooperation device,
the to-be-transmitted data sent by the cooperation device.
23. The communications device according to claim 22, wherein a frequency band used for
transmission on the sidelink is a licensed frequency band or an unlicensed frequency
band.
24. The communications device according to claim 23, wherein when the unlicensed frequency
band is used for transmission on the sidelink, a channel used for transmission on
the sidelink comprises one or more candidate sidelink channels, and the transceiver
is further configured to send, in a common sidelink subframe, information used to
indicate whether the to-be-transmitted data is correctly received, wherein the common
sidelink subframe is a subframe at a preset location that is on the sidelink channel
and that is agreed on between the communications device and the cooperation device.
25. A communications system, wherein the communications system comprises the communications
device according to any one of claims 13 to 18 and the communications device according
to any one of claims 19 to 24.